We recommend replacing nursing bottles every 6-12 months for hygiene reasons, irrespective of the material used, if sterilised by boiling, steam, or chemicals. Consider replacing the bottles if you notice stubborn milk stains, scratches, or discoloration. While UV sterilisation is suitable, it might cause premature aging upon repeated use. To prevent damage, maintain a 1-inch distance from the UV steriliser’s inner wall when sterilising the bottles.